Perpendicular magnetic recording has been developed in part to achieve higher recording density than is realized with longitudinal recording devices. A PMR write head typically has a main pole layer with a small surface area (pole tip) at an ABS, and coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through the pole tip and enters a magnetic medium (disk) adjacent to the ABS. Magnetic flux is used to write a selected number of bits in the magnetic medium and typically returns to the main pole through two pathways including a trailing loop and a leading loop. The trailing loop has a trailing shield structure with first and second trailing shield sides at the ABS. The second (PP3) trailing shield arches over the driving coil and connects to a top yoke that adjoins a top surface of the main pole layer near a back gap connection. The leading loop includes a leading shield with a side at the ABS and that is connected to a return path (RTP) proximate to the ABS. The RTP extends to the back gap connection (BGC) and enables magnetic flux in the leading loop pathway to return from the leading shield at the ABS and through the BGC to the main pole layer. The double write shield (DWS) design that features the leading and trailing loops was invented for adjacent track erasure (ATE) improvement by reducing stray field in side shields and in the leading shield. Accordingly, a PMR head has a great advantage over LMR in providing higher write field, better read back signal, and potentially much higher areal density.
Perpendicular magnetic recording has become the mainstream technology for disk drive applications beyond 150 Gbit/in2. Accordingly, the critical dimensions (CDs) of the PMR writer are continually shrinking. For example, the track width (TW) in today's writers is typically in a range of 10 nm to 100 nm. To achieve areal density in a hard disk drive (HDD) beyond 2 terabytes per platter (TBPP) for conventional PMR, dual PMR writer schemes have been proposed where the better writer is selected and then integrated into a HGA to provide improved area density capability (ADC) mean and sigma values. There may be <10 microns in cross-track writer-writer spacing (WWS) for a dual PMR writer at the ABS.
While it is advantageous to retain the heater coil layout from a single PMR scheme where a first DFH heater coil is in the read head, and a second DFH (WDFH) heater coil is placed in the write head, the symmetric (parabolic) heater protrusion profile with the close-point for WG protrusion at track center in a dual PMR writer may cause magnetic spacing loss, depending on the size of WWS, which results in burnishing of the recording head. Thus, there is a need for an improved dual PMR writer design that enables better control of WG protrusion than provided by a single WDFH heater coil without having adverse thermal-mechanical implications or system level integration issues in a head gimbal assembly (HGA).